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NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 

Subcontract Report 

NREL/SR-560-36129 

May 2005 

Boundary Analysis for H2

Production by Fermentation 

July 2001 — September 2004 

T. Eggeman 

Neoterics International 

Lakewood, Colorado 
National Renewable Energy Laboratory 

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov 

Operated for the U.S. Department of Energy 

Office of Energy Efficiency and Renewable Energy 

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337

Subcontract Report 

NREL/SR-560-36129 

May 2005

Boundary Analysis for H2

Production by Fermentation 

July 2001 — September 2004 

T. Eggeman 

Neoterics International 

Lakewood, Colorado 

NREL Technical Monitor: M.K. Mann 

Prepared under Subcontract No. LCO-1-31055-01 
This publication was reproduced from the best available copy 

Submitted by the subcontractor and received no editorial review at NREL

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Introduction 

 The Hydrogen Program of the U.S. Department of Energy is examining novel methods 

for hydrogen production. One potential means for hydrogen production is the fermentation of 

glucose or other carbohydrates: 

C6H12O6 + 6 H2O => 12 H2 + 6 CO2, ∆Go

 = -16 kJ/mol 

(Glucose) 

Theoretically, up to 12 moles of hydrogen can be produced per mole of glucose consumed. 

 This report presents a boundary analysis for this approach. A simplified overall material 

and energy balance along with order-of-magnitude economics are presented. 

Design Summary 

 The design basis assumed a hydrogen production rate of 50 MMSCFD at 435 psig. 

Figure 1 is a block flow diagram. The simplified material balance and utilities summary were 

computed with the assistance of Aspen Plus 10.2 (files: E0312b). 

The base case assumes a yield of 10 moles of hydrogen per mole of glucose, with a 

glucose concentration of 3 wt% in feed to fermentation. The remaining fraction of the glucose is 

assumed to either be unconverted or diverted into cell mass production. No cost or value was 

associated with disposal of the cell mass stream. Also, no costs for nitrogen and other nutrient 

sources are included in the analysis. 

 A battery limits addition to an existing biorefinery is envisioned. The host facility will 

provide glucose, water, utilities and other infrastructure as a variable operating cost for the new 

facility. The fixed capital investment is limited to the battery limits unit; in other words, no 

capital for upgrades to the host facility’s infrastructure is included in the base case. 

 Conceptually any carbohydrate source could be used as a feedstock for the fermentation. 

Corn starch hydrolyzate, juices from sugar cane or sugar beet processing, wood fiber 

hydrolyzates from pulp mills, or biomass hydrolyzates from agricultural resides, energy crops 

and other biomass sources are among the many possible sources. Many of these potential 

feedstocks would actually produce a mixture of sugars upon hydrolysis. To simplify the analysis, 

I assumed that carbohydrate was present only in the form of glucose. The presence of a mixed 

carbohydrate feedstock and its impact on the design were not considered in this preliminary 

analysis. 

 A few statements are needed to put the scale of this plant into perspective. By today’s 

standards, a 50 MMSCFD hydrogen plant would be a large, but not world-scale, industrial 

hydrogen production facility. The amount of carbohydrate required to feed this facility roughly 

corresponds to the total carbohydrate present in 2,000 metric tons per day of corn stover. This 

feed rate corresponds to the rate used in the 2002 NREL Design Case for bioethanol production 

(1). The NREL design case assumes corn stover is collected from a 50 mile radius around the 

1
plant and is projected to produce 69.3 MMgal of ethanol per year. In terms of starch hydrolyzate 

from corn, the projected feed rate corresponds to a grind rate of roughly 80,000 bushels per day. 

This would be considered a medium scale corn dry milling facility or a small scale corn wet 

milling facility. 

Results 

 Table 1 summarizes the projected fixed capital investment. Individual cost items were 

obtained as follows: 

1) Fermentation Unit – Taken to be the same as for the fermentation unit in the 2002 NREL 

Design (1) (i.e. costing by analogy with a similar process) 

2) Raw Gas Compressor - Estimated using Questimate, a commercially available software 

program for generating equipment costs. 

3) PSA – Estimated on H2 production rate and internal cost curves. 

4) Cell Recovery Unit – A detailed definition of the unit is not available; a reasonable 

capital allocation was assumed. 

5) Other – The balance of plant was assumed to be 50% of the identified equipment. 

 The total fixed capital is projected at $73.6MM, or a fixed capital investment of 

$1.47MM per MMSCFD of H2 production. For comparison, the standard industry “rule-ofthumb” for fixed capital costs for production of hydrogen by steam methane reforming are 

$1.00MM per MMSCFD of H2 in this capacity range, although recent facilities have had slightly 

lower requirements (2). 

 Table 2 summarizes projected plant level operating costs. Glucose is the major operating 

cost driver. The base case assumed that glucose was available at $0.05 per lb (dry). This is 

approximately the value placed on dilute, unfinished sugar streams in today’s corn processing 

facilities. The US DOE goal for the cost of sugar in biomass hydrolyzates is $0.07 per lb in Year 

2012. Long term goals for US DOE are to reduce cost of biomass derived sugars into the $0.03-

$0.05 per lb range. 

Steam, electricity, and depreciation are other important operating cost drivers. Steam 

costs are driven by the assumed need to heat sterilize the fermentation media. Steam usage is 

sensitive to the glucose concentration in the media. Electricity costs are driven by the power 

needs of the raw gas compressor. The simulation assumed the inlet suction pressure of the raw 

gas compressor was 14.7 psia. Pressurized operation of the fermentation vessels may reduce the 

compression work requirements and compression capital, at the expense of increased capital for 

fermentation. 

2
 Table 3 summarizes projected revenues. Nearly 95% of the revenues are derived from 

hydrogen. The byproduct fuel gas, derived from the PSA tail gas, was valued on a heating value 

basis using industrial natural gas as the proxy. 

 The discounted cash flow calculations use the rational pricing rather market pricing 

method. For rational pricing, the hydrogen sales price required for a 10% after tax real internal 

rate of return for the project under the assumptions of 100% equity financing and 40 years of 

operation is calculated. The calculated required price does not reflect the market value of the 

hydrogen product. 

Figure 2 displays the projected cumulative cash flows. Breakeven occurs between Year 8 

and Year 9 of operation. Faster times to breakeven can be had by either increasing the required 

discount rate (i.e. making the required hydrogen selling price higher) or by increasing the amount 

of debt financing. 

 Figure 3 displays contributions to the calculated required price for hydrogen. Glucose 

feedstock, utilities, and capital are the major drivers. 

Sensitivity Analysis 

Figure 4 shows the effect of hydrogen yield and the cost of glucose on the feedstock cost 

component. The base case assumed 10 moles H2 per mole glucose and $0.05 per lb (dry) for 

glucose. The effect on the required hydrogen prices of changing these assumptions can be 

estimated using Figure 4 to adjust for the feedstock portion of the required hydrogen price. Note 

that other cost components such as capital and non-feedstock operating costs are not included in 

this figure. One opportunity for reduced hydrogen price is finding waste feedstocks or taking 

advantage of R&D advancements in the biomass feedstock preparation area. If the feedstock 

could be obtained for $0.03/lb of glucose, the required hydrogen price would be reduced to 

$1.60/kg. At a zero feedstock price (representing a niche-market waste), the required hydrogen 

price is reduced to $0.90/lb. 

Figure 5 shows the sensitivity of the required hydrogen price with respect to variations in 

fixed capital. Since the economics are dominated by the cost of carbohydrate, the effect of 

variations in fixed capital are somewhat muted. 

Glucose concentration in the fermentation feedstock will affect both the amount of steam 

required for heat sterilization and the capital cost for the fermentation unit. Calculating the exact 

projections for the effect of glucose concentration on the required hydrogen price is involved. A 

rough estimate can be generated by just looking at the impact on steam usage. Lowering the 

glucose concentration in the feed from 3 wt% to 1.5 wt% doubles the amount of water present in 

the feed, which in turn doubles the heat load for sterilization, or adds another ~$0.23 per kg H2 to 

the required hydrogen price. 

Figure 6 shows the sensitivity of the required hydrogen price with respect to variations in 

the required internal rate of return. The figure shows that the required internal rate of return has 

a significant impact on the projected economics. 

3
Conclusions 

 The cost of carbohydrate and the yield of hydrogen from carbohydrate appear to drive the 

economics in the “best case” scenario considered in this report. It is questionable whether 

deployment of resources needed to develop this method of hydrogen production is justified, 

given the fact that the long term goals of the Hydrogen Program require costs lower than those 

projected by this analysis. The use of lower-priced feedstocks could reduce the required selling 

price of hydrogen to as low as $0.90 – 1.60/kg hydrogen. An assessment of the availability of 

these feedstocks and the real potential for R&D to produce low-cost sugars is needed. 

References 

(1) Aden, A., Ruth, M., Ibsen, K., Jechura, J., Neeves, K., Sheehan, J., Wallace, B, Montague, 

L., Slayton, A., Lukas, J., “Lignocellulosic Biomass to Ethanol Process Design and 

Economics Utilizing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis 

for Corn Stover”, NREL/TP-510-32438, June 2002. 

(2) Fleshman, J.D. in Chapter 6.2 of Meyers, R.A. (ed.), Handbook of Petroleum Refining 

Processes, 2nd ed., McGraw-Hill, 1997. 

4
Table 1 - Fixed Capital Summary

$MM (2000)

Direct

Fermentation Unit 10.0

Raw Gas Compressor 11.3

PSA 10.9

Cell Mass Recovery Unit 4.0

Other 18.1

Total 54.4

Indirects

Engineering & Design 4.4

Construction Expense 5.4

Contractor's Fee 2.7

Total 12.5

Contingency

Depreciable Fixed Capital w/o Contingency 66.9

Contingency 6.7

Depreciable Fixed Capital 73.6

Non-Depreciable Fixed Capital 0.0

Total Fixed Capital 73.6

Fixed Capital, $MM/MMSCFD of H2 1.47

5
Table 2 - Operating Cost Summary

(Plant Level)

Variable $/yr $/kg H2

Raw Materials

Glucose 40,789,314 1.1594

Subtotal 40,789,314 1.1594

Utilities

Steam 7,993,798 0.2272

Electricity 7,507,863 0.2134

Other 799,380 0.0227

Subtotal 16,301,041 0.4634

Other 735,916 0.0209

Subtotal 735,916 0.0209

Total Variable 57,826,271 1.6437

Fixed

Labor 1,248,000 0.0355

Maintenace Labor 919,894 0.0261

Maintenance Materials 1,839,789 0.0523

Property Taxes & Insurance 1,471,831 0.0418

General and Adminstrative 249,600 0.0071

Depreciation (10 yr SL) 7,358,155 0.2092

Total Fixed 13,087,269 0.3720

Cash Costs 63,555,385 1.8066

Operating Costs 70,913,541 2.0157

Table 3 - Revenue Summary

Item $MM (2000)/yr $/kg H2

Hydrogen 73.08 2.0772

Fuel Gas 4.12 0.1171

Total 77.20 2.1944

6
Stream Summary

American Standard Units

Stream Feed H2 Fuel KO Cell Water

Product Gas Liquid Mass

Temperature, F 70 110 110 110.6 110 110

Pressure, psia 14.7 449.7 20.0 14.7 14.7 14.7

Components, lb/hr

 H2 0 11,067 1,953 0 0 0

 CO2 0 0 142,080 0 47 0

 Water 3,763,850 0 492 13,547 77,760 3,613,880

 Glucose 116,408 0 0 0 19,440 0

Total, lb/hr 3,880,258 11,067 144,525 13,547 97,247 3,613,880

SI Units

Stream Feed H2 Fuel KO Cell Water

Product Gas Liquid Mass

Temperature, C 21.1 43.3 43.3 43.7 43.3 43.3

Pressure, kPa 101.4 3100.5 137.9 101.4 101.4 101.4

Components, kg/hr

 H2 0 5,020 886 0 0 0

 CO2 0 0 64,446 0 21 0

 Water 1,707,256 0 223 6,145 35,272 1,639,230

 Glucose 52,802 0 0 0 8,818 0

Total, kg/hr 1,760,057 5,020 65,555 6,145 44,111 1,639,230 

Utilities Summary

Steam Electricity

Duty, Steam, Power, Power,

Exchanger MMBtu/hr lb/hr Item hp (Shaft) kW (Motor)

H-101 185.9 185,899.6 C-400 24,677.1 20,446.4

Total 185,899.6 P-100 184.1 152.6

Other 1,000.0

Total 21,598.9

Feed 

Prep 

Cell 

Recovery 

Raw Gas 

Compression 

Fermentation 

PSA 

Feed

Water

Cell 

Mass 

KO 

Liquid 

Fuel

H2 Product

Figure 1 – Design Summary 

7
Figure 2 - Cumulative Cash Flow

-100.

0

100.

200.

300.

400.

500.

-5 0 5 10 15 20 25 30 35 40

Year of operation

Cumulative After Tax Income, $MM

Breakeven

Figure 3 - Category Cost Contributions

$0.36

$1.17

$0.00

$0.16

$0.50

-$0.11

-$0.2

$0.0

$0.2

$0.4

$0.6

$0.8

$1.0

$1.2

$1.4

Capital Cost Feedstock Cost Other Raw Material Fixed O&M Cost Other Variable

O&M Cost

Contribution to Required Hydrogen Selling Price ($/kg)

Byproduct

Credit

8
Figure 5 - Sensitivity wrt Fixed Capital

$1.90

$1.95

$2.00

$2.05

$2.10

$2.15

$2.20

$2.25

$2.30

$2.35

0 20.0 40.0 60.0 80.0 100.0 120.0

Fixed Capital, $MM (2000)

Required H2 Price, $/kg

Design

Figure 4 - Sensitivity of Feedstock Cost Component vs. Fermenation Yield and Glucose Cost

(Cost includes affect of H2 loss in PSA; No capital or non-feedstock operating costs are included)

0

1

2

3

4

5

6

0 2 4 6 8 10 12

Fermentation Yield, mol H2/mol Glucose

Raw Material Cost, $/kg H2

Glucose @ $0.03 per lb (dry)

Glucose @ $0.05 per lb (dry)

Glucose @ $0.07 per lb (dry)

Glucose @ $0.10 per lb (dry)

Design

9
Figure 6 - Effect of IRR on Required H2 Price

1.90

2.10

2.30

2.50

2.70

2.90

3.10

0 5 10 15 20 25 30

Internal Rate of Return, After Tax - Real

Required H2 Price, $/kg

Design

10
Bioprocess • Energy • Chemicals • Polymers 

NEOTERICS INTERNATIONAL 

Using Technology to Create Business Innovation 

303-358-6390 2319 S. Ellis Ct. 

time@frii.com Lakewood, CO 80228

March 12, 2004 

Margaret Mann 

National Renewable Energy Laboratory 

1617 Cole Boulevard, MS 1613 

Golden, CO 80401 

Dear Maggie: 

 Enclosed is a conceptual design and order-of-magnitude economic analysis for the 

production of hydrogen by fermentation of carbohydrates under the following design basis: 

 Production Rate: 120,480 kg H2/day 

Plant Type: Battery limits with no capital required for 

OSBL expansions 

 Utilities: Purchased from host facility 

 Fermentation Yield, moles H2 per mole Glucose 10 

 Cost of glucose, $/lb (dry) 0.05 

 Nitrogen and other nutrient sources None 

 Waste treatment costs None 

The results of the economic analysis are: 

Fixed Capital, $MM (2000) 73.6 

Required H2 Price, $/kg H2 2.08 

where the required H2 price is defined as the price required for a 10% after-tax real internal rate 

of return under the assumption of 100% equity financing and 40 years of plant operation. 

The results projected by this study should be considered as a “best case” scenario. The 

assumed technical performance could only be achieved after significant long-term research. 

Sensitivity analysis shows major economics drivers include: fermentation yield, cost of 

glucose, fixed capital, glucose concentration in the fermentation and various financial 

assumptions. 

Sincerely, 

Tim Eggeman, Ph.D., P.E. 

11
Bioprocess • Energy • Chemicals • Polymers 

Addendum 

NEOTERICS INTERNATIONAL 

Using Technology to Create Business Innovation 

303-358-6390 2319 S. Ellis Ct. 

time@frii.com Lakewood, CO 80228

July 29, 2004 

Margaret Mann 

National Renewable Energy Laboratory 

1617 Cole Boulevard, MS 1613 

Golden, CO 80401 

Dear Maggie: 

This letter is a follow up on several issues raised at the US DOE Workshop on Hydrogen 

Production via Direct Fermentation held on June 9, 2004, in Baltimore, MD. 

1) Operating Capacity Factor: The original analysis assumed an 80% operating capacity 

factor. I re-ran the economics using a 95% operating capacity factor. The required H2

selling price drops from $2.077 per kg to $1.955 per kg. This change only makes a small 

change in the economics, thus the main conclusions of the report are unaffected. 

2) Fermentation Assumptions: The report is an order-of-magnitude estimate for the 

economics of hydrogen production assuming significant improvements in the technology. 

I assumed that the fermentation was anaerobic, the feed sugar concentration was 30 g/l 

and the capital cost would be similar to that projected for the fermentation section of 

bioethanol plants processing a similar amount of feedstock. The current NREL design 

model for bioethanol production uses a simultaneous saccharification and fermentation 

design. The rate controlling step is hydrolysis of the complex carbohydrates into simple 

fermentable sugars, so volumetric productivity is independent of fermentation kinetics. It 

is too early to speculate on the relative rates of hydrogen production by fermentation vs. 

saccharification kinetics, but in essence I’ve assumed the fermentation kinetics will be 

faster than saccharification. 

3) Sanitation Requirements: I envision the sanitation needs for this plant to be similar to 

those of today’s ethanol production facilities. The feeds would be heat sterilized, but the 

plant would not require extreme levels of sterility. The assumed sugar feed concentration 

is fairly low for an industrial fermentation. Higher sugar concentrations would reduce 

steam usage for sterilization, but may lead to issues with feed inhibition. 

4) Cell Mass Value: I assigned a zero value to the cell mass. The value of the cell mass 

depends upon whether it can be sold or has to be treated as a waste. Cell mass from 

many industrial fermentations today is often sold into animal feed markets. For example, 

the cell mass from a corn dry mill ends-up in the DDGS product used primarily for 

ruminant feeds, while the cell mass from citric acid production can sometimes be sold as 

a poultry feed ingredient. On the other hand, if the cell mass cannot be sold then it has to 

be treated as a negative value waste. Digestion, compositing, landfill, and incineration 

12
 

are some possible options for treatment. Assigning a zero value to the cell mass is a 

reasonable assumption for a preliminary analysis since its value is unknowable at this 

time. 

5) Nutrient Costs: I assumed zero costs for nutrients. It is difficult to estimate costs since 

nutrient requirements of the organism are unknown and the nutrient content of the 

feedstock is unknown. As a comparison, current bioethanol models project a nutrient 

cost of about $0.03 per gallon. 

6) Plant Scope: The analysis assumed a battery limits plant that purchased utilities from a 

host facility. Capital costs for a stand-alone plant could easily be double the costs for a 

battery limits plant. This, of course, will vary quite a bit depending upon the details of 

the situation. 

Please let me know if there are any other issues that need to be addressed. 

Sincerely, 

Tim Eggeman 

13
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DE-AC36-99-GO10337 

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Boundary Analysis for H2 Production by Fermentation 

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NREL/SR-560-36129 

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HY04.1390 

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T. Eggeman 

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Neoterics International 

2319 S. Ellis Ct. 

Lakewood, CO 80228 

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LCO-1-31055-01 

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NREL Technical Monitor: M.K. Mann 

14. ABSTRACT (Maximum 200 Words)

This report, prepared for DOE’s Hydrogen, Fuel Cells & Infrastructure Technologies Program, presents a boundary 

analysis for the production of hydrogen via fermentation of glucose or other carbohydrates. The Program’s hydrogen 

production cost target goals cannot be met due to the high feedstock cost. The potential for lower-cost sugars to 

meet cost targets should be investigated. 

15. SUBJECT TERMS

Hydrogen Production; Fermentation; Economic Analysis 

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